A commercially available folding knife includes a handle and a blade body which are pivotally connected with each other. The blade body is rotatable about its pivoting location to be out of the handle or received into the handle. After the folding knife is folded, it has a smaller size to facilitate the user to carry and it is also safer for the user to carry because the blade body is received into the handle. Therefore, compared with other non-foldable knife, the folding knife has better convenience and is more suitable for divers, outdoorsmen, or Military and police personnel.
Generally, in order to improve convenience of operating the folding knife, manufacturers develop an auxiliary tool which includes an elastic sheet to push the blade body. Please refer to FIGS. 1A and 1B. The folding knife 1 includes a blade body 11, a handle 13 and an elastic sheet 15. An end of the blade body 11 is pivotally connected to an end of the handle 13, and the blade body 11 is rotatable about its pivoting location, so that the other end of the blade body 11 (that is, a tip) can be exposed out of the handle 13 or received into the handle 13. The blade body 11 includes a push pin 111 disposed adjacent to the end thereof and out of the handle 13, and the user can push the push pin 111 by finger. The elastic sheet 15 has an end located adjacent to a position where the handle 13 and the blade body 11 are pivotally connected with each other, and other end extended towards the other end of the handle 13 and located adjacent to the other end of the handle 13. Please refer back to FIG. 1A. When the blade body 11 is completely received into the handle 13, the elastic sheet 15 is abutted with the end of the blade body 11 to apply a first force L1 on the blade body 11, as shown by a dashed arrow L1 of FIG. 1A. While being applied by the force L1, the blade body 11 can be rotated to the handle 13, thereby more tightly positioning the blade body 11 into the handle 13. Please refer back to FIG. 1B. When the blade body 11 is forced to rotate out of the handle 13 by a predetermined angle (about 4 to 8 degrees), the elastic sheet 15 may apply a second force L2 on the blade body 11, as shown by a dashed arrow L2 of FIG. 1B. Subject to the second force L2, the blade body 11 is rotated out of the handle 13, thereby completely rotating the blade body 11 out of the handle 13 instantly. When wanting to push the blade body 11 received in the handle 13 to rotate out of the handle 13, the user just pushes the push pin 111 by thumb to rotate the blade body 11 out of the handle 13 by a predetermined angle (about 4 to 8 degrees), so that the blade body 11 can instantly be rotated out of the handle 13, similar to a conventional spring knife.
Furthermore, some manufacturers replace the elastic sheet by a volute spring, to be the auxiliary tool for pushing the blade body. The folding knife described below includes some elements the same as that of the conventional knife, so these elements shown in FIG. 2 are labeled by the reference numbers the same as that of FIG. 1A. Please refer to FIG. 2. A volute spring 21 is assembled at a position where the blade body 11 and the handle 13 are pivoted with each other. The volute spring 21 always applies a force on the blade body 11 to rotate the blade body 11 out of the handle 13. When the blade body 11 is completely received into the handle 13, a constraining unit (not shown in FIG. 2) on the handle 13 can constrain the blade body 11 and apply other force on the blade body 11, thereby positioning the blade body 11 in the handle 13. As a result, when wanting to rotate the blade body 11 received in the handle 13 out of the handle 13, the user just pushes the push pin 111 on the blade body 11 to overcome the other force applied by the constraining unit, thereby releasing the blade body 11 from being constrained by the constraining unit. At this time, subject to the force applied by the volute spring 21, the blade body 11 is quickly rotated out of the handle 13.
The conventional folding knife may be easy to use, but if its blade body is unable to hold in a complete unfolded state or a completely received state reliably, it may cause safety problem. For this reason, the knife manufacturers design various lock mechanisms, such as liner lock mechanism, frame lock mechanism, back lock mechanism or axis lock mechanism, in order to improve safety of the folding knife. To summarize, safety of the folding knife in use is always a topic attracting people's attention, and what is need is to develop a new folding knife having better safety, a concise structure, and more convenience in use.